The Fresh Loaf

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Heat Mat...

pmitc34947's picture

Heat Mat...

Has anyone used a heat mat (pictured below) to keep their sourdough starter at a continuously warm temperature? The temperature in my house runs 62 - 72 F. I am finding I have very sluggish starter and am thinking of new ways to keep my starter at 76 - 80 F and active for successful bakes. My refrigerator is recessed into the wall, so the ideal location on the top is unavailable to me. One idea I have come across is to wrap the starter jar in a heat mat. This is often used to incubate seeds and plants. I have also seen it advertised as good to use in brewing kombucha, larger mats are used in the brewing of beer.

sadkitchenkid's picture

That might actually be pretty genius. If it's used for planting, then you know it *shouldn't* get hot enough to kill your starter. You should check in every now and then though because heat mats are often unreliable. Most are designed to be used with a thermostat and they can suddenly burn up. I have a heat mat that I used for my snake's tank (it's also used for planting) and knowing that there is a possibility for it to suddenly burn up and hurt the little fella, I also bought a thermostat to regulate the temperature. I know someone who uses heat mats to put under proofing dough!

So in summary I'd say that this is a great idea, but I'd definitely advise you to only use it for the specific time that you want to get your starter activated and bubbly because leaving a heat pad on indefinitely without a thermostat can potentially be dangerous. 

good luck!

pmitc34947's picture

The heat mat arrived yesterday. I wrapped it around my sourdough starter bottle with two rubber bands. Four hours later, I had a bubbly mixture, though the sourdough was not passing the float test. I think further tests are needed following a new refresh. Before bed, I wrapped the heat mat around another bottle filled with room temperature water with a thermometer in the bottle. The next morning the thermometer reads 91 F.  

clazar123's picture

I have never seen such a small heating pad!

Some alternate ideas:

A heating pad for humans has a controller on it-not quite a thermostat (just has low-med-hi) but it is designed to be on for a long period of time. Also it is a bit larger and can even be bought in an extra large size.

Seedling heating mats also come in various sizes.

Temp. is critical for the activity of a culture. My kitchen temp dropped into the mid 60'sF and my countertop kefir culture started to sleep! Instead of a 18-24 ripeness cycle, it is now on a 24-30 hr cycle and much more sour.

Stay warm!

DanAyo's picture

At this time I'm using my proofing box for my starter. It is kept out at room temp. But it is tied up with my starter all the time, leaving it unavailable for other doughs.

I checked Amazon, and considering ordering the following to test out.


and also a seed strip

I saw cheaper versions, but I like the ratings on these.

The controller might also be used for a heating pad for proofing purposes.

I'm thinking about the possibility of placing my small starter container into a larger one that would be filled with water. Then heat the outside of the larger container. My thought is that this might distribute the heat more evenly. I've used a heating page and the bottom of the container gets a little too warm for me.

What do you think?



DanAyo's picture

I was extremely interested in your post concerning the heat mat. I’m not really great at originating ideas but I really get into tweaking them {;-)

This is my concept and after initial testing things look good. I use a small juice glass (6oz) for my starter. I don’t mix much starter because I hate throwing flour away. My starter is 5:15:25, so it weighs in @45g. The starter triples and the glass is tall enough to accommodate. This is what I’ve done. I get a jar a little larger than my starter jar and put enough water in it to just reach about 3/8” from the top. I place the starter jar into the larger jar with the water. No need to seal the top of the starter jar because everything is sealed inside the larger one. In the screw on lid for the large jar I made 2 holes. One for the temperature probe and the other for testing accuracy with a thermometer. I’m still checking the temperature accuracy, but it is close.

Note - the temperature probe (black cable) is difficult to see. It is behind the thermometer shaft.

The controller reads72.5 and the Thermapem 72F. What remains to be seen is how well the heat mat works when the temperatures get colder. It is mild right now.

Please let me know your findings thus far.


old baker's picture
old baker

I put my dough in the oven with the lights on.  After a few hours, the temp is ~90 F.

Babs3696's picture

I've been using a heating pad for my starter and it has worked great! I turn the heating pad thermostat to the lowest setting then put several layers of paper towels on the pad to lower the heat a bit so that the heat is not directly in contact with my starter. Then I place my starter on the heating pad and just leave it until the next feeding. It's always nice and bubbly a few hours after feeding.